Dumnonia

Dumnonia was a Brythonic kingdom in present-day Devon, England which existed from the late 4th to late 8th centuries AD. Dumnonia was named for the Celtic Dumnonii people, and the Britons of Dumnonia resisted incursions by the Germanic Anglo-Saxons. In 632, the Dumnonians defeated a Mercian siege of Exeter and inflicted heavy casualties on the Saxons, but the Dumnonians were defeated by Wessex at Peonnum in 658, permanently losing their eastern lands. From 813 to 822, King Egbert of Wessex conquered insular Dumnonia, leaving behind the rump state of Cornwall, or "West Wales", named for its Brythonic inhabitants.